Compress the same image using two dimensional DCT (dct2) with 6.25% of the dct coefficients retained, the others are set to zeros. (no windows, it is Global DCT). You need to sort the coefficients from largest to smallest, then retain the largest 6.25% and set the rest to zero. A simpler way is to find the location; 0.0625*(size), set all values beyond this location to zero. Use idct2 to get the reconstructed image. Find the rms and psnr. Display the output.